These may be in particular, but not exclusively, scraper rings of small thickness, each consisting of two split and flat rings which may have a thickness of 4/10th mm, commonly termed "rails", and separated by a spring-ring, also split, of special shape, commonly termed "spacer", these members being constituted of a steel alloy and having, once superimposed and placed into the corresponding groove of the piston, a total thickness on the order of 2 mm. The resilient spacer may have different configurations and may comprise for example, on the radially inward side, a corrugated peripheral step, by virtue of which this spacer, through its radial resilience, exerts an outward radial pressure on the two rails, necessary in order to produce the leaktightness around the piston when it is placed in its cylinder.
FIGS. 1 through 4 of the accompanying drawings show by way of example the constituent members of such a scraper piston ring.
FIG. 1 shows a rail 1 seen from above and FIG. 2 a spacer 2 also seen from above, with its steps 3, FIG. 3 being a profile view of this spacer 2. FIG. 4 shows in cross section the scraper piston ring constituted by the stacking of two rails 1 and of a spacer 2, the radially outward part of this piston ring corresponding to the left part of the figure. Owing to the small thickness of the rails 1 and the special profile of the spacer 2, their fitting into the grooves of the pistons has hitherto been carried out manually.